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Prevalence, risk factors and spatial analysis of liver fluke infections in Danish cattle herds.

Olsen A, Frankena K, Bødker R, Toft N, Thamsborg SM, Enemark HL, Halasa T - Parasit Vectors (2015)

Bottom Line: The spatial analysis suggested significant clustering of positive and negative herds.Additionally, risk of being infected with F. hepatica was higher in non-dairy herds of medium size (≥30 and < 100) when compared to dairy and large (≥100) cattle herds.Fasciolosis was found to be associated with both herd and environmental factors where the infection was influenced by local factors that clustered geographically.

View Article: PubMed Central - PubMed

Affiliation: Quantitative Veterinary Epidemiology group, Wageningen University, Wageningen, The Netherlands. abbey_olsen@hotmail.com.

ABSTRACT

Background: Fasciola hepatica, a trematode parasite (liver fluke), infects a wide range of host species causing fasciolosis. The disease is prevalent world-wide and causes considerable economic losses to the livestock industry. Fasciolosis is regarded as an emerging food-borne zoonosis. To promote awareness among farmers and to implement strategies to control the infection, this study examined the prevalence, spatial distribution and risk factors for F. hepatica infection in Danish cattle herds.

Methods: A retrospective population based study was performed using meat inspection data of approximately 1.5 million cattle slaughtered in the period 2011 to 2013. Annual cumulative prevalence of recorded liver fluke findings was calculated for each year. Global and local spatial cluster analysis was used to identify and map spatial patterns of F. hepatica positive and negative herds to explore environmental indicators of infection. Herd level, trade and environmental risk factors were evaluated for association with infection using logistic regression. Herd infection status as predicted from the final risk factor model was compared with the observed status using heat maps to assess how well the model fitted the observed spatial pattern.

Results: During the investigated period (2011-2013), an increase in annual herd prevalence was noted (2011-25.6%; 2012-28.4%; 2013-29.3%). The spatial analysis suggested significant clustering of positive and negative herds. Presence of streams, wetlands and pastures on farms showed a significant association with the presence of infection in cattle herds. Buying animals from positive herds was a risk factor on conventional farms. Additionally, risk of being infected with F. hepatica was higher in non-dairy herds of medium size (≥30 and < 100) when compared to dairy and large (≥100) cattle herds. The observed spatial pattern could be reproduced by predictions of the risk factor model.

Conclusions: This study showed an increase in annual herd level prevalence (2011 to 2013) indicating that an increasing proportion of herds are infected with F. hepatica infection every year in Denmark. Fasciolosis was found to be associated with both herd and environmental factors where the infection was influenced by local factors that clustered geographically.

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Related in: MedlinePlus

Heat maps of observed (a) and predicted (b) status ofFasciola hepaticainfection in Danish cattle herds (n = 16,626) where areas coloured in red and blue indicate hot (RR ≥ 1.0) and cold spots (RR < 1.0), respectively. The insert in Figure 2 a shows a SatScan map of significant spatial local clustering of infected (red) and non-infected (blue) herds.
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Fig2: Heat maps of observed (a) and predicted (b) status ofFasciola hepaticainfection in Danish cattle herds (n = 16,626) where areas coloured in red and blue indicate hot (RR ≥ 1.0) and cold spots (RR < 1.0), respectively. The insert in Figure 2 a shows a SatScan map of significant spatial local clustering of infected (red) and non-infected (blue) herds.

Mentions: As spatial autocorrelation was recognized, local clusters were identified and mapped. The results from the circular scan showed that 6,126 herds were situated in hot spots where the RR for F. hepatica infection was 1.4; whereas 1,055 herds were situated in cold spots where the RR was 0.6. The plotting of hot spots on a map of Denmark revealed a strong overall spatial trend with concentration of high RR for F. hepatica infection around the North and Central Jutland region of Denmark (Figure 2 a, insert). Whereas, plotting of cold spots revealed low RR for F. hepatica infection in the Southern Jutland, Funen, Islands and the Zealand region.Figure 2


Prevalence, risk factors and spatial analysis of liver fluke infections in Danish cattle herds.

Olsen A, Frankena K, Bødker R, Toft N, Thamsborg SM, Enemark HL, Halasa T - Parasit Vectors (2015)

Heat maps of observed (a) and predicted (b) status ofFasciola hepaticainfection in Danish cattle herds (n = 16,626) where areas coloured in red and blue indicate hot (RR ≥ 1.0) and cold spots (RR < 1.0), respectively. The insert in Figure 2 a shows a SatScan map of significant spatial local clustering of infected (red) and non-infected (blue) herds.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4374337&req=5

Fig2: Heat maps of observed (a) and predicted (b) status ofFasciola hepaticainfection in Danish cattle herds (n = 16,626) where areas coloured in red and blue indicate hot (RR ≥ 1.0) and cold spots (RR < 1.0), respectively. The insert in Figure 2 a shows a SatScan map of significant spatial local clustering of infected (red) and non-infected (blue) herds.
Mentions: As spatial autocorrelation was recognized, local clusters were identified and mapped. The results from the circular scan showed that 6,126 herds were situated in hot spots where the RR for F. hepatica infection was 1.4; whereas 1,055 herds were situated in cold spots where the RR was 0.6. The plotting of hot spots on a map of Denmark revealed a strong overall spatial trend with concentration of high RR for F. hepatica infection around the North and Central Jutland region of Denmark (Figure 2 a, insert). Whereas, plotting of cold spots revealed low RR for F. hepatica infection in the Southern Jutland, Funen, Islands and the Zealand region.Figure 2

Bottom Line: The spatial analysis suggested significant clustering of positive and negative herds.Additionally, risk of being infected with F. hepatica was higher in non-dairy herds of medium size (≥30 and < 100) when compared to dairy and large (≥100) cattle herds.Fasciolosis was found to be associated with both herd and environmental factors where the infection was influenced by local factors that clustered geographically.

View Article: PubMed Central - PubMed

Affiliation: Quantitative Veterinary Epidemiology group, Wageningen University, Wageningen, The Netherlands. abbey_olsen@hotmail.com.

ABSTRACT

Background: Fasciola hepatica, a trematode parasite (liver fluke), infects a wide range of host species causing fasciolosis. The disease is prevalent world-wide and causes considerable economic losses to the livestock industry. Fasciolosis is regarded as an emerging food-borne zoonosis. To promote awareness among farmers and to implement strategies to control the infection, this study examined the prevalence, spatial distribution and risk factors for F. hepatica infection in Danish cattle herds.

Methods: A retrospective population based study was performed using meat inspection data of approximately 1.5 million cattle slaughtered in the period 2011 to 2013. Annual cumulative prevalence of recorded liver fluke findings was calculated for each year. Global and local spatial cluster analysis was used to identify and map spatial patterns of F. hepatica positive and negative herds to explore environmental indicators of infection. Herd level, trade and environmental risk factors were evaluated for association with infection using logistic regression. Herd infection status as predicted from the final risk factor model was compared with the observed status using heat maps to assess how well the model fitted the observed spatial pattern.

Results: During the investigated period (2011-2013), an increase in annual herd prevalence was noted (2011-25.6%; 2012-28.4%; 2013-29.3%). The spatial analysis suggested significant clustering of positive and negative herds. Presence of streams, wetlands and pastures on farms showed a significant association with the presence of infection in cattle herds. Buying animals from positive herds was a risk factor on conventional farms. Additionally, risk of being infected with F. hepatica was higher in non-dairy herds of medium size (≥30 and < 100) when compared to dairy and large (≥100) cattle herds. The observed spatial pattern could be reproduced by predictions of the risk factor model.

Conclusions: This study showed an increase in annual herd level prevalence (2011 to 2013) indicating that an increasing proportion of herds are infected with F. hepatica infection every year in Denmark. Fasciolosis was found to be associated with both herd and environmental factors where the infection was influenced by local factors that clustered geographically.

Show MeSH
Related in: MedlinePlus